Oxytocin is a hormone and a neurotransmitter that is involved in childbirth and breast-feeding. It is also associated with empathy, trust, sexual activity, and relationship-building.

It is sometimes referred to as the "love hormone," because levels of oxytocin increase during hugging and orgasm. It may also have benefits as a treatment for a number of conditions, including depression, anxiety, and intestinal problems.

Oxytocin is produced in the hypothalamus, a part of the brain. Females usually have higher levels than males.

Fast facts on oxytocin

Here are some key points about oxytocin. More detail is in the main article.

Oxytocin is produced in the hypothalamus and released during sex, childbirth, and lactation to aid reproductive functions.

It has physical and psychological effects, including influencing social behavior and emotion.

Oxytocin is prescribed as a drug for obstetric and gynecological reasons and can help in childbirth.

Research shows that it may benefit people with an autistic spectrum disorder (ASD), anxiety, and irritable bowel syndrome (IBS).

What is oxytocin?

Oxytocin is important during childbirth and breast-feeding.

Oxytocin is a neurotransmitter and a hormone that is produced in the hypothalamus. From there, it is transported to and secreted by the pituitary gland, at the base of the brain.

It plays a role in the female reproductive functions, from sexual activity to childbirth and breast feeding. Stimulation of the nipples triggers its release.

During labor, oxytocin increases uterine motility, causing contractions in the muscles of the uterus, or womb. As the cervix and vagina start to widen for labor, oxytocin is released. This widening increases as further contractions occur.

Oxytocin also has social functions. It impacts bonding behavior, the creation of group memories, social recognition, and other social functions.

Oxytocin as a drug

Oxytocin is used as a prescription drug under the brand name Pitocin. Under medical supervision, an oxytocin injection is sometimes used to start birth contractions or strengthen them during labor, and it helps reduce bleeding after delivery. Side effects include a rapid heartbeat and unusual bleeding.

If too much oxytocin is delivered too rapidly, it can lead to a rupture of the uterus.

Oxytocin can also be given to make the uterus contract and control bleeding after a delivery or a termination.

It can be used medically to induce a termination or complete a miscarriage.

The love hormone?

In 2012, researchers reported that people in the first stages of romantic attachment had higher levels of oxytocin, compared with non-attached single people. These levels persisted for at least 6 months.

Sexual activity has been found to stimulate the release of oxytocin, and it appears to have a role in erection and orgasm. The reason for this is not fully understood, but, in women, it may be that the increased uterine motility may help sperm to reach their destination. Some have proposed a correlation between the concentration of oxytocin and the intensity of orgasm.

Oxytocin and emotion

Oxytocin appears to play a role in social interaction and relationships between people.

When oxytocin enters the bloodstream, it affects the uterus and lactation, but when it is released into certain parts of the brain, it can impact emotional, cognitive, and social behaviors.

One review of research into oxytocin states that the hormone's impact on "pro-social behaviors" and emotional responses contributes to relaxation, trust, and psychological stability.

Brain oxytocin also appears to reduce stress responses, including anxiety. These effects have been seen in a number of species.

The hormone has been described as "an important component of a complex neurochemical system that allows the body to adapt to highly emotive situations."

Is it that simple?

In 2006, investigators reported finding higher levels of oxytocin and cortisol among women who had "gaps in their social relationships" and more negative relations with their primary partner. The participants were all receiving hormone therapy (HT) following menopause.

Animal studies have found high levels of both stress and oxytocin in voles that were separated from other voles. However, when the voles were given doses of oxytocin, their levels of anxiety, cardiac stress, and depression fell, suggesting that stress increases internal production of the hormone, while externally supplied doses can help reduce stress.

Clearly, the action of oxytocin is not straightforward.

A review published in 2013 cautions that oxytocin is likely to have general rather than specific effects, and that oxytocin alone is unlikely to affect "complex, high-order mental processes that are specific to social cognition." The authors also point out that a willingness to collaborate is likely to be driven by anxiety in the first place.

Nevertheless, oxytocin does appear to be associated with social behavior, including maternal care, bonding between couples, sexual behavior, social memory, and trust.

Behavioral effects

Delivering oxytocin through a nasal spray has allowed researchers to observe its effects on behavior.

In 2011, research published in Psychopharmacologyfound that intranasal oxytocin improved self-perception in social situations and increased personality traits such as warmth, trust, altruism, and openness.

In 2013, a study published in PNASsuggested that oxytocin may help keep men faithful to their partners, by activating the reward centers in the brain.

In 2014, researchers published findings in the journal Emotionsuggesting that people saw facial expression of emotions in others more intensely after receiving oxytocin through a nasal spray.

Psychiatric therapy

Scientists have proposed that it might help improve interpersonal and individual wellbeing, and that it could have applications for people with some neuropsychiatric disorders.

They believe it could help people who avoid social interaction, and those who experience persistent fear and an inability to trust others.

Children with autism could benefit from oxytocin, say some researchers. In 2013, a small study suggested that oxytocin levels in the brain affected how 17 children perceived a series of social and non-social images.

Oxytocin may also play a role in anger management. Research has indicated that certain polymorphisms of the oxytocin receptor (OXTR) gene are associated with an increased tendency to react angrily to situations.

In particular, differences in OXTR gene expression appear to affect the regulation of the relationship between alcohol and aggressive behavior.

Uses

Oxytocin appears to increase the release of prostaglandin E2 (PGE2) in cells lining the intestine. This helps to encourage the repair of intestinal injury and to protect against such injury.

If this is confirmed, oxytocin could be a useful therapy for preventing chemo-radiotherapy-induced intestine injury, and it could be used to treat irritable bowel syndrome (IBS).

Risks

The role of oxytocin is complex and not easy to pin down.

While it appears to enhance bonding and the forming of communities, it may also encourage the formation of "in-groups" and "out-groups," giving rise to envy, prejudice, and possibly aggression.

Participants in a 2014 study were more likely to lie for the benefit of others in the same group after receiving oxytocin. The findings, said researchers, could help with "providing insight into when and why collaboration turns into corruption."

More investigation is needed to understand the complexity of oxytocin and what it does.

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